83. Remove Duplicates from Sorted List：
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode* deleteDuplicates(ListNode* head) {
ListNode *dup = NULL;
ListNode *cur = head;
if(cur == NULL || cur->next == NULL) return head;
ListNode *nxt = cur->next;
while(nxt != NULL){
if(cur->val == nxt->val){
ListNode *dup = nxt;
nxt = nxt->next;
cur->next = nxt;
delete dup;
}else{
cur = nxt;
nxt = nxt->next;
}
}
return head;
}
};
2. Add Two Numbers：
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
ListNode* ret, *tmp;
int carry = 0, sum=0;
ret = tmp = new ListNode(0);
while(carry||l1||l2){
sum = carry;
if(l1)sum+=l1->val;
if(l2)sum+=l2->val;
carry = sum/10;
tmp->val = sum%10;
if(l1)l1 = l1->next?l1->next:NULL;
if(l2)l2 = l2->next?l2->next:NULL;
if(!l1 && !l2 && !carry)return ret;
tmp->next = new ListNode(0);
tmp=tmp->next;
}
return NULL;
}
};
21. Merge Two Sorted Lists：
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
if(!l1) return l2;
if(!l2) return l1;
ListNode *head, *retList;
if(l1->val <l2->val){
retList = head = l1;
l1 = l1->next;
}
else{
retList = head = l2;
l2 = l2->next;
}
while(l1 && l2){
if(l1->val <l2->val){
head->next = l1;
l1 = l1->next;
head = head->next;
head->next = NULL;
}
else{
head->next = l2;
l2 = l2->next;
head = head->next;
head->next = NULL;
}
}
if(!l1) head->next = l2;
if(!l2) head->next = l1;
return retList;
}
};
206. Reverse Linked List：
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode* reverseList(ListNode* head) {
if(head == NULL || head->next == NULL) return head;
ListNode* pre = NULL;
ListNode* cur = head;
ListNode* nx = cur->next;
while(nx != NULL){
cur->next = pre;
pre = cur;
cur = nx;
nx = nx->next;
}
cur->next = pre;
return cur;
}
};
148. Sort List
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode* sortList(ListNode* head) {
ListNode*p = head;
ListNode*q = NULL;
int temp = 0;
if(head == NULL) return head;
for(; p!=NULL; p=p->next)
for(q=p->next; q!=NULL; q=q->next){
if(p->val > q->val){
temp = p->val;
p->val = q->val;
q->val = temp;
}
}
return head;
}
};
19. Remove Nth Node From End of List
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode* removeNthFromEnd(ListNode* head, int n) {
if(head == NULL || n == 0) return head;
ListNode* slow = head;
ListNode* fast = head;
ListNode* pre = head;
if(fast->next == NULL) return NULL; //[1] 1
while(n>0){ //if n, slow will just point to the nth
fast = fast->next;
n--;
}
while(fast != NULL){
fast = fast->next;
pre = slow;
slow = slow->next;
}
pre->next = slow->next;
//if pre==slow==head [1,2] 2
if(pre == slow) return head->next;
return head;
}
};
141. Linked List Cycle
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
bool hasCycle(ListNode *head) {
ListNode* slow = head;
ListNode* fast = head;
while(fast && fast->next){
slow = slow->next;
fast = fast->next->next; //2step
if(slow == fast) return true;
}
return false;
}
};
160. Intersection of Two Linked Lists
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode *getIntersectionNode(ListNode *headA, ListNode *headB) {
ListNode* p1 = headA;
ListNode* p2 = headB;
while(p1 != p2){
p1 = p1?p1->next:headB;
p2 = p2?p2->next:headA;
}
return p1;
}
};
203. Remove Linked List Elements
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode* removeElements(ListNode* head, int val) {
if(head == NULL) return head;
ListNode* p = head;
while (p->next != NULL){
if(p->next->val == val){
ListNode *tmp = p->next;
p->next = p->next->next;
delete tmp;
}
else{
p = p->next;
}
}
if(head->val == val)
head = head->next;
return head;
}
};
237. Delete Node in a Linked List
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
void deleteNode(ListNode* node) {
ListNode* p = node->next;
node->val = p->val;
node->next = p->next;
delete p;
}
};